Effect of 3-D step topography on ground motion

This paper simulates the different types of three-dimensional step topography effects on ground motion due to a point source by using spectral element method. Level topography and several different 3-D step topographies are simulated, which shows that the 3-D step topographies have an important impact on seismic waves. The effect from the intersecting lines of step slopes with upper level is different from that with the lower level. Moreover, the characteristics of various topographies are described using snapshots of the ground motions; the measuring line diagrams of the intersecting lines of step slope with upper level and those with the lower level demonstrate that the waveform diagrams of 3-D step topography have obvious scattering waves relative to level topography. Also it shows that the values on the upper and lower measuring lines on 3-D step topography are amplified relative to level topography. On the waveforms of lower measuring lines the amplification ranges from 1.1 to 1.5, and that is from 0.9 to 1 on the waveforms of upper measuring lines. These studies describe the impact of step topography at the edge of the mountain due to a point-source earthquake and give the respective positions’magnification of the 3-D step topography relative to level topography, providing a basis for forward engineering studies.